Fix limit testing after 1762f674ccb571e6 ktrace commit.
The previous:
if ((uoff_t)uio->uio_offset + uio->uio_resid > lim)
signal(....);
was replaced with:
if ((uoff_t)uio->uio_offset + uio->uio_resid < lim)
return;
signal(....);
Making (uoff_t)uio->uio_offset + uio->uio_resid == lim trip over the
limit, when it did not previously.
Unbreaks running 13.0 buildworld.